Telephone system



May 27, 1930. J. l. BELLAMY 1,760,626

TELEPHONE SYSTEM Filed May 25, 1928 2 Sheets-Sheet 1 Jul-m LBeHam y- 7,1930. .1. I. BELLAMY I 7 1,760,626

TELEPHONE SYSTEM Filed May 25, 1928 2 Sheets-Sheet 2 Jul-m lEeZZam Patented May 27, 1930 aurrnn stares 5P ATE T l oFFwE system but is concerned more particularly 6 JQQNIQBELLAMY, ianooirrrntn, rLtrNoIs, ASSIGNOR TO RESERVE HOLDING com- 6 rnnYaor senses-em t, MISQQURI, A conroanrron or DELAWARE TELEPHONE SYSTEM Application ea m 25,

Thepresent invention relates to-telephone with improvements in sending devices used therein and the object, generally stated, is the product on oflnewandimproved arrange ments for securing a more uniform operation a e of the apparatus governed by sending equipershave cometo be known-as directors.

It, is well known that automatic switching,

apparatus used in automatic telephone sys tems operates best when theimpulsing circuit through which theimpulses are transmitted toythe switching "apparatus varies-in resistance through only relatively narrow limits, and that ifthe resistance varies through limits that are too great, the automatic s witching apparatus often fails to respond properly. The greatest difiicujlty is experienced inmultiofhce systems wherein trunk lines varying widely in resistance are encountered. i It has been found in practice that if arrangements canbedevisedfor maintaining the resistance of the impulsing circuit practically constant, a greatsaving can beeffected in the time and expensemequired to maintain the rigid adjustment which isnecessaryin case the impulsing resistance is not kept within rather closehmits. a 7

When register senders, less in number than the trunk lines with which theyare associ ated, areemployed in multi-ofice automatic telephone systems .to receive digits transmitted from calling stations and to retransmit digitsto the automatic switching appa ratus, it becomes economical owing to the relativelysma'll number of register senders to provide; arrangements in the register senders tocompensate for thevarying resistances of the trunk lines over which impulses are transmitted. a

It is an object of this invention to provide arrangements in a, register sender automatically effect ve to add a local resistance to the impulse circuit of each low-resistance trunk l neover wh ch impulses are transm tted sufficient to, ra se the total reslstance to apredetermined standard value.

'made. I a menth ThQ/ IIIVGI IUOI L has been apphedi to register senders for use, 1n multl-ofiice auto- 1925. s r ixnbmasoazz.

It is a further object to provide arrangea a result of theswitching operation performed in response to the preceding digit m ay be GeneraZ description a Referring now to the accompanying drawings comprising Figs; 1 and 2, they show by means of the usual circuit diagrams "asufficient amount of apparatus in a telephone system embodying the features of the invention to enable theiinventionto be understood.

7 Fig. I shows a telephone line leading from the automatic substation A to the exchange and terminating therein the individual line switch C, which has access to the first selector Diby way of the trunk circuitTC which is individual to the selector D. The selector D has access to various local and linter-ofiice trunksas indicated The register sender se lector DS is individual to the trunk circuit TC andhas access to a plurality of register senders such asthe one shown in to which it has access over conductors '9'1'9 t. 6 Only a small portionlof the register sender is shown in the drawings. "This register sender may be the same as the sho n in the Stehlik Patent 1,640,473, granted August 30, 1927, except for the additionof compensating relay 281 284 and the associated circuit connections as will belater ezr plained; I i

willbe noted that Fig. '1 of the present disclosure and Fig. 1 of the: above Stehlik patentare very similar to one another. The line switch C of the present disclosure may be the same as the :line switch of thepatent. the same beingtrue of the selectorD. The

Detailed description In order that the invention may be understood best, a detailed description of the operation of the apparatus shown will now be given. For this purpose it will be assumed that the subscriber at substation A desires that a connection be extended to another subscriber whose line terminates in the same ofliceg. a

Localcall When the subscriber at substationA removes his receiver, the line switch C operates in the usual manncr'in search of an idle trunk. Assuming that the trunk extending through the trunk circuit TO to the selector D. is the first one found to be idle, theline switch C seizes this trunk comprising conduc tors 27, whereupon line relay 31 operates over the calling line and closes a circuit for release relay Release relay 32 operates and places ground on conductor 26 at a sepa-.

. rate armature so asto maintain the established connection. At its two lower armatures, rfelay 32causes the director selector DS to search for an idle register sender in the usual manner. When an idle sender is reached, the one shown in Fig.2 for example, the hunting action of the switch DS ceases and relay 81 operates and completes the connection to the wipers 8790, therebyextending a connectionto the register sender of Fig. 2 over conductors 91-94. l 7

When the wipers 87 and 88 are connected up, the usual line relay (not shown) of the selector D pulls up over conductor 91 and 92' ofthe register sender, preparing the selector D for operation. It may be'pointed out that the circuit of the said line relay includes the normally-closed contacts controlled by the inner lowerarmature of pick-up relay 202, upper Winding of relays 281284, and armature. 200 and its resting contact in parallel with sending contacts 233 .Since the first digit to be transmitted is to the selector D over local cable connections of relatively low resistance, the current flow is suflicient to oplera-te all of the marginalrelays 281284, w ereupon each relay at its upper contacts inserts the associated resistance in the branch circuit and prepares a locking circuit for itself 'at its lower'contacts.

The setting of the registering portion on the register sendernow takesplace responsive to the control exercised by means of the usual dial at the substation A through the medium of line relay 31 of the trunk circuit T C, which transmits the impulses from ground throughthe back contactof its inner lower armature over theassociated conductor,

and through contacts of relay 81 to impulse conductor 94 by way of wiper 90 of the switch DS.

After the setting of the registering'apparatus has proceeded to the proper point, the sending operation is started. The first step in the sending operation, as will be learned from the Stehlik patent above referred to, is

the pulling up of the pickup relay 202 so as 200. At itslower armature, relay 202 closes a locking circuit through contacts of stop relay 203 for the operated relays 281284, While at its inner lower armature it alters the impulse circuit so as to include the resistances associated with relays 281284L instead of the upper windings of these relays. Since all of the relays are operated due to the fact that a local switch is being controlled, each of the resistances is cut in the impulsing circuits as to bring the total resistance up to the required standard.

When the required number of impulses have been transmitted, stop relay 203 pulls up and shunts the impulse circuit at armature 211, at the same time bringing about the usual circuit changes including the circuit changes necessary to *restore' the sending switch to normal. These: circuit changes are accomplished by contacts of relay 203 which are not essential to the present invention and are not shown in the present drawing. As a further result of the energization of stop relay 211, it opens the locking circuit of relays 28l284,whereupon these relays all fall back.

After the sending switch has been restored to normal, pick-up relay 202 falls back and stop relay 203 falls back a moment later and prepares'the locking circuit on'the compensating relays again.

Upon the falling back of pick-up relay 202, the relays 281-284, which are thereupon reinserted in the circuit at the contacts controlled by the inner lower armature of this relay, reset themselves for the second digit. Since, according to the previous assumption, the subscriber at substation A is calling a local number, the resistance of the impulse circuit is not materially greater than in the first place and all of the compensating relays pull up again, as they do following each digit.

It may be mentioned that the switchthrough operation which takes place at the end of the transmission of the last digit is efi'ected when a ground potential is applied over conductor 94, through wiper 90 of the switch DS, lower contacts of relay 81, lower armature, operated of relay 31, to switchthrough relay 33, which locks itself to release trunk conductor 26 at its inner armature, at the same time completing a holding bridge across the conductors extending to the selector D through the right hand repeating coil windings and the lower contacts of relay At its two inner armatures, relay 33 brings about the release of the selector DS by dropping back relay 81 and I further point in the I The falling back of first digit. When the pick-up relay back following across the talking conductors.

test circuit of the switch. relay 81frees the register sender and removes the impulse bridge from The release of the connectlon taking place C'QZZ to 077506 A Assume now that the subscriber at substa tion A is calling a subscriber at oifice A and that the operation has proceeded as hereinbefore described up to the sending out of{tl1e alls the sending out of this the reoperation of relays 281-28l takes place on the basis of current flow over the inter ofiice trunk line from the calling ethics to oihce A. It may be assumed for purpose of illustration that this current; flow is reduced to such an extentithat relay 284:, which is the I fourth relay of the set, y 25,

tration that the present does not pull up. In this case, when the sending of the next digit starts upon the reoperation of pick-up relay 202, only relays 281%283 are operated and only three of the four compensating resistances are cut in. a i i It may be assumed forthe purpose of illuscall is for a sub-office of office A and that theso-called series holding circuit is employed in ofiice Aon thetrunk lines leading to the sub-oiiice, so that the impulse-circuit resistance is still further increased to that of a trunk line from oiiice A to the sub-office. In this case, it may bearbitrarily assumed that the current flow iscut down to such an extent that only relays 281 and 282 operate when pick-up relay 202 again falls back.

Call to ofiice B Assuming now that a call is being extended from the line of substation A in the manner hereinbefore described to a line terminating in oiiice B, and assuming further that ofice B is a considerable distance away from the originating oihce so that the total resistance in the impulsing circuit is already up -to standard value, when pick-up relay 202 falls back atter'the first digit has been sent out, all of the compensating relays 281*284 remain non-operated and noadditional resistance is cut in.

From the foregoing description it will be seen that the variation in resistance of the impulsing circuit is compensated for in any one of four steps and that when no compensation is needed, none is made, giving five d1tferent conditions. It will be understood that more or fewer compensating relays may be used, but the number shown is considered to be typical. i

It will be understood of course that the Qcuit over lIiittl impuls digit,

sanie mangan se forcompensating"for reeaaut may be em- I and 32 when the calling subscriber hangs up his receiver. i 10 "Wh t ela m i 1 hon system, i an impulse cir hltrains of impulses are transo nittediincidental to t lie positioning of auto- '0 switching, apparatus, resistance compe sati g apparatus associate'chwithsaid in'g circuit,fand testingmeans con- "trolledoversaid impulse circuit for adjusting the compensatlng apparatus in accordance-wi l the resistance of the clrcuitQ I In atelephone system, an impulse circult'over whichtra ns of, impulses are transmitted ncidental' to the positioning of I automaticlswitching apparatus, resistance compensating apparatus, associated with said impulsing circuit, andtesting meansl'included in saidapparatus and controlled over said impulse circuitbetween series of impulses.

3. In a telephone system wherein trains of impulses are transmitted over impulse circuits incidental to the positioning of automatic switching apparatus, a portion of an impulse circuit arranged to be supplemented u by other portions of impulse circuits to form several complete impulse circuits during the setting up of a telephone connection, and automatic compensating means associated with the first impulse circuit portion and lco automatically controlled thereover to com: pensate for resistance variations in the said supplementing portions.

4. In an impulse compensator for use in a telephone system wherein series of impulses are transmitted incidental to the positioning of automatic switching apparatus, resistance elements, testing means controlled over an impulse circuit for preparing to bring said elements into circuit, and a switching device i for excluding the testing means and for ineluding resistance elements into circuit as predetermined by the position of the testing means after its operation over the impulse circuit.

5. In an impulse circuit for use in connection with the positioning of automatic switching apparatus, two branches for said circuit, one branch including marginal relay, apparatus, the other branchincluding resistance apparatus controlled by the marginal relay apparatus.

6. In an impulse circuit for use in connection with the positioning of automatic switching apparatus, two branches for said circuit, one branch including marginal relay apparatus, the other branch including resistance apparatuscontrolled by the marginal impulse series and for completing it through 4 the resistancebranch during impulse series.

7. In a switching'system, means including automatic switching aiparatus for building up a connection by lin ng successive extensions to a line, a control circuit including said 7 line and the extensions are they are linked thereto, means for controlling said apparatus over said circuit, and means controlled over said circuit betweensuccessive extensions of said line for alterin a characteristic of said line to compensate orthe' linked extensions.

8. In combination, automatic. switching apparatus operable in stages, a control circult and means for operating said apparatus in stages thereover, and means including testing apparatus applied to said control circult between stages for maintaining a characteristic of said control circuit within predetermined limits. V

In witness-whereof, I hereunto. subscrlbe my name this twenty-first day of May, A. D.

JOHN I. BELLAMY. 

